We don't leave behind letters and diaries anymore. We leave inboxes and Facebook accounts. But will your loved ones have access to that information?

Before her 21-year-old daughter died in a sledding accident in early 2007, Pam Weiss had never logged on to Facebook. Back then, social-networking sites were used almost exclusively by the young. But she knew her daughter Amy Woolington, a UCLA student, had an account, so in her grief Weiss turned to Facebook to look for photos. She found what she was looking for and more. She was soon communicating with her daughter's many friends, sharing memories and even piecing together, through posts her daughter had written, a blueprint of things she had hoped to do. "It makes me feel good that...